Depolarized light scattered near the gas–liquid critical point of Xe, SF6, CO2, C2H4, and C2H6

Abstract

We report an experimental study of depolarized Rayleigh light scattered at 90° by two isotropic fluids (xenon and sulfur hexafluoride) and three anistropic fluids (carbon dioxide, ethane, and ethylene) near their respective gas–liquid critical points. All measurements were performed along the critical isochore, in the single phase region, that is to say for T≳Tc. The depolarization ratios, as shown by theory, are separable into two contributions. Far from the critical temperature single scattering of light is predominant but near the critical point double and multiple scatterings become the main phenomena. From measurements of polarized intensities in the temperature range corresponding to double scattering, the cross sections or the compressibility factors were calculated when a choice of a theoretical expression for the Rayleigh ratio was made.